" The Splitting Chisel (Fig. 13e) is used chiefly on the softer stratified stones, and sometimes on fine architec tural carvings in granite.
" The Plug, a truncated wedge of steel, and the Feathers, of half-rounded malleable iron (Fig. 14), are used in splitting unstratified stone. A row of holes is made with the drill (Fig. 15) on the line on which fracture is to be made; in each of these holes two feathers are inserted and the plugs are driven in between them. The plugs are then gradually driven home by light blows of the hand hammer on each, in succession until the stone splits." 44. Methods of Finishing the stones used in building are divided into three classes, according to the finish of the surface, viz.: " 1. Rough stones that are used as they come from the quarry.
" 2. Stones roughly squared and dressed.
" 3. Stones accurately squared and finely dressed.
" In practice the line of separation between them is not very distinctly marked, but one class merges into the next.
" Un.squared Stones. This class covers all stones which are used as they come from the quarry, without other preparation than the removal of very acute angles and excessive projections from the figure. The term backing, which is often applied to this class of stone, is inappropriate, as it properly designates material used in a certain relative position in the wall, whereas stones of this kind may be used in any position.
" Squared class covers all stones that are roughly squared and roughly dressed on beds and joints. Tlie dressing is usually done with the face hammer or axe, or, in soft stones, with the tooth hammer. In gneiss, it may sometimes be necessary to use the point. The distinction between this class and the third lies in the degree of closeness of joints. Where the dressing on the joints is such that the distance between the general planes of the surfaces of adjoining stones is inch or more the stones properly belong to this class.
" Three subdivisions of this class may be made, depending on the character of the face of the stones.
"(a) Quarry faced stones are those whose faces are left untouched as they come from the quarry.
"(b) Pitch-faced stones are those on which the arris is clearly defined by a line beyond which the rock is cut away by the pitching chisel, so as to give edges that are approximately true (Fig. 16).
" Drafted Stones are those on which the face is surrounded by a chisel draft, the space within the draft being left rough (Fig. 17). Ordinarily, however, this is done only on stones in which the cutting of the joints is such as to exclude them from this class.
" In ordering stones of this class, the specifications should always state the width of the bed and end joints which are expected, and also how far the surface of the face may project beyond the plane of the edge. In practice, the proportion varies from 1 to 6 inches. It should also he specified whether or not the faces are to he drafted. " Cut class covers all squared stones with smoothly dressed beds and joints. As a mile, all the edges of cut stones are drafted, and between the drafts the stone is smoothly dressed. The face, however, is often left rough where the construction is massive. " In architecture, there are a great many ways in which the faces of cut stone may be dressed, but the following are those which will usually be met with in engineering work.
" it is necessary to remove an inch or more from the face of a stone, it is clone by the pick or heavy point until the projections vary from inch to 1 inch. The stone is then said to be rough-pointed. (Fig. 18.) " a smoother finish is desired, rough-pointing is followed by fine-pointing, which is clone with a fine point. Fine pointing is used only where the finish made by it is to be final, and never as a preparation for a final finish by another tool.
" is only a speedy method of pointing, the effect being the same as fine-pointing, except that the dots on the stone are more regular. The variations of level are about s inch, and the rows are made parallel. When other rows at right angles to the first are introduced, the stone is said to be cross-crandalled.